This invention relates to an electronic heat amount meter comprising a computer operating on the analog principle, a volumeter, and means for connecting signal processing devices thereto.
An already known electronic heat amount meter substantially comprises an electronic computer, operating on the analog principle, and a mechanical volumeter. This meter is supplied from the power system.
Because of the basic design of this meter, certain limits are set to its application since it does not indicate the instantaneous value of the heat consumption and the rate of flow of the heat carrier, nor is it provided with suitable connecting elements for further signal processing devices, for example, recorders. In practice, this alone eliminates the possibility of controlling open and/or closed loop control members which would be provided adjacent the installation. In addition, for economical reasons, a battery power supply cannot be considered, since the current consumption is relatively high.
Another known electronic heat amount meter also comprises a computer which, however, operates on the digital principle, and a mechanical volumeter. In this case, the computing unit is powered by a battery. This, it is true, permits an operation independent of the power line, but the provided battery has only a limited capacity so that an exchange is necessary from time to time.
Finally, still another known electronic heat amount meter comprises an electronic computer operating on the digital principle, and a mechanical volumeter. The computer is supplied from the power line. Even though digital computers may be useful for certain applications, they are not suitable for the purposes of the present invention. It is also disadvantageous, or, at least, of little value, for the present invention to be dependent only on the power line.
Primarily, however, the just mentioned known designs of heat amount meters are not satisfactory in view of the basic concept of their mechanical volumeters, since they involve the risk of a not inconsiderable wear due to impurities contained in the heat carrier and also precipitations therefrom, particularly at higher temperatures. According to experience, the wear begins after only a relatively short service time and results in inaccuracies of measurement.
It is obvious that such inaccuracies in measurement also entail inaccuracies in the determination of charging for the consumed heat quantities. In addition, with the known design of volumeters, the occurrence of creeping quantities, which are due to friction and adulterate the result of measurement even if to a limited extent, cannot be excluded.
A further problem with the known volumeters is that their admissible operational temperature is limited to about 90.degree. C. For an operation at higher temperatures (long distance heating systems operate within a range of, for example, up to 130.degree. C.) only expensive constructions are available.
Because of the wear to be expected in the known constructions of volumeters, not inconsiderable maintenance costs must be taken into account, since the devices must be periodically not only checked and cleaned but also perhaps even exchanged. It is further clear that the permanently necessary maintenance creates a need for qualified personnel and suitable material, devices and tools.
As already mentioned above, the known electronic computers of this kind do not indicate the instantaneous values of heat consumption nor the volumetric flow (rate of flow). Exactly this, however, is required from non-mechanical meters in order to be able to make adjustments in the system, for example, to limit the rate of flow to a maximum. Limits are set to the application or use of the meters of the prior art also by the fact that they are not available for influencing other necessary open and/or closed loop control members of the system.
As to the power supply for heat amount meters of the prior art, the connection to the power line results in not inconsiderable installation costs, which further increase the expenditures to an undesirable extent. The drawback of the known devices of being dependent on the power line (assume, for example, a power failure) may be, it is true, avoided by using batteries, but relatively narrow limits are set for the power supply from such energy accumulators, particularly for electronic computers operating on the analog principle, because of the continuous energy consumption and also in view of the limited power capacity. In addition, the connection of a heat amount meter to the power source must be secure against misuse, i.e. independent of the respective private meter, and tamperingproof from the outside.
Not least for remedying the insufficiencies of mechanical volumeters mentioned in the foregoing and known in the art, volumeters of the non-mechanical type have also been developed. Such meters make use, for example, of ultrasonics, of the inductivity of an electric field, of isotope radiation, of frequencies of eddies separating from a body placed in the fluid, as well as of the effective head drop through an orifice, plate, etc.
For example, U.S. Pat. Nos. 1,267,758 and 1,948,234, French Patent No. 1,247,036, and British Patent No. 663,083 show meters in which the differential pressure is produced by an orifice. Such orifices, however, have numerous disadvantages. Thus, they provide only a small measuring range, and the measuring accuracy is very unstable due to contamination and wear of the orifice. In these meters, the differential pressure signal is converted to an electric signal through more or less complicated mechanical systems, or liquid-based systems, which are affected by friction entailing additional inaccuracies and which, as far as the liquid-based systems are concerned, must be handled very carefully during transportation.
These devices have been tested and proved satisfactory. However, for normal application, they are not, or not quite, suitable as heat amount meters since they are, as compared to the heat amount meters of the prior art discussed above, considerably more expensive. As for their supply with power, there also applies what has been said in the foregoing about the individual known heat amount meters.